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Renal function in children with hypercalciuria
1Department of Pediatrics, Osmangazi University Faculty of Medicine, Eskişehir.
Insights
Children with hypercalciuria often show normal renal function but may have subtle tubular injury. Urinary N-acetyl-beta-D-glucosaminidase (NAG) is a sensitive marker for detecting this renal tubular injury in pediatric hypercalciuria cases.
Area of Science:
- Pediatric Nephrology
- Renal Physiology
- Biomarker Discovery
Background:
- Hypercalciuria is a common pediatric condition linked to abdominal pain, hematuria, enuresis, and kidney stone formation.
- It arises from either a renal tubular calcium leak or increased intestinal calcium absorption.
- Assessing renal functional impairment in children with hypercalciuria is crucial for understanding potential long-term consequences.
Purpose of the Study:
- To investigate the presence of renal functional impairment in children diagnosed with hypercalciuria.
- To evaluate the utility of urinary N-acetyl-beta-D-glucosaminidase (NAG) as a sensitive marker for renal tubular injury in this population.
Main Methods:
- Screened 298 children for hypercalciuria using the urinary calcium/creatinine (UCa/UCr) ratio.
- Evaluated renal function in 18 children with hypercalciuria (UCa/UCr > 0.18) and compared them to a healthy control group.
- Measured creatinine clearance, osmolar and free water clearances, fractional sodium excretion, tubular phosphorus reabsorption, and urinary NAG excretion.
Main Results:
- Hypercalciuria was detected in 6.4% of the screened children, with significantly higher daily calcium excretion compared to controls.
- Standard renal function tests (creatinine, osmolar/free water clearances, fractional sodium excretion, tubular phosphorus reabsorption) showed no significant differences between hypercalciuric children and controls.
- Urinary NAG excretion, normalized for creatinine, was significantly elevated in children with hypercalciuria, indicating tubular injury.
Conclusions:
- Children with hypercalciuria typically exhibit normal overall renal function based on conventional tests.
- Urinary NAG is a sensitive biomarker for detecting subclinical renal tubular injury in pediatric hypercalciuria.
- NAG measurement offers a valuable tool for identifying early tubular damage in children with hypercalciuria, even with normal renal function studies.
Abstract:
Hypercalciuria is a common problem causing symptoms such as abdominal pain, hematuria and enuresis, and leading to stone formation. It results from a renal tubular calcium "leak" or intestinal hyper-reabsorption of calcium. This study was performed to determine whether renal functional impairment was present in children with hypercalciuria. The study group comprised 298 children who were screened for hypercalciuria by means of urinary calcium/creatinine (UCa/UCr) ratio. The renal functions of 18 children (6.4%) detected as having hypercalciuria with Ca/Cr ratios of greater than 0.18 in their spot urines were evaluated. Results were compared with those of the healthy control group. The rate of hypercalciuria did not very significantly between the boys and girls (p > 0.05). The mean value of daily calcium excretion was 6.42 + 3.93 mg/kg/day in the children with hypercalciuria, which was significantly different from that of the control group (p < 0.01). When the values of creatinine, osmolar and free water clearances, fractional excretion of sodium and tubular reabsorption of phosphorus were compared between the patient and control groups, the difference was not significant (p > 0.05). Urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion, which was described as the creatinine ratio, was significantly higher in the children with hypercalciuria. These findings suggest that in the presence of normal renal functional studies in children with hypercalciuria, tubular injury can be detected by NAG, which is a more sensitive marker of renal tubular injury.